su_marke.gif (2405 bytes)

David Strömberg


WH 2008 Analysis


Home
IIES
New
People
Publications
Seminars
About
Institute for
International Economic Studies
Stockholm University
SE-106 91 Stockholm
SWEDEN

Phone: +46 8 16 43 77
Fax: +46 8 16 14 43
E-mail: info@iies.su.se
Webmaster:
www@iies.su.se

Last updated,

 October 1, 2008

The Bradley effect

I have estimated the Bradley effect based on 431 elections for House, Senator and Governor, 1998-2006, containing 26 black candidates. The effect is 2-3 percent of the two-party vote share. See Strömberg (2008) for details and discussion.

Below are some election statistics in case the Bradley effect for Obama is of similar size as that estimated in the 1998-2006 races discussed above.

November 3

The table below show election statistics if Obama will suffer a Bradley effect of the same 2-3 percent size as the average (Democratic and Republican) candidates for the 22 House, Senate and Governor races 1998-2006 for which I have data.

Probability of winning

Obama McCain
52% 48%

Expected vote share

Obama McCain
50.0% 50.0%

Expected number of electoral votes

Obama McCain
271 269

 

November 3, black Democratic candidates

The estimated Bradley effect for black Democratic candidates lowers Obama's win chances as of November 3 from 87 to 68 percent. The effect is is -1.2 percent with a standard error of 1.6, so not statistically different from zero. Still, the uncertainty about the size of the Bradley effect makes Obama's lead uncertain.

I find this by using the full distribution of the estimated coefficient. I take a 100 draws from this distribution and estimate the average statistic.

Probability of winning

Obama McCain
68% 32%

Expected vote share

Obama McCain
51.3% 48.7%

Expected number of electoral votes

Obama McCain
297 241

 

October 29

The number below were computed using the 2-3 percent Bradley effect.

Probability of winning

Obama McCain
53% 47%

Expected vote share

Obama McCain
49.9% 50.1%

Expected number of electoral votes

Obama McCain
273 265

The polling data and vote data for elections with one black candidate is available here.